Acrylonitrile polymers stabilized with certain beta-hydrocarbonoxypropionitriles



United States Patent ACRYLONITRILE POLYMERS STABILIZED WITH CERTAIN BETA-HYDROCARBONOXYPROPIONI- TRILES George W. Stanton and Forrest A. Ehlers, Walnut Creek,

Calif., assignors to The Dow Chemical Company, Midland, Mich., a corporation of Delaware No Drawing. Application June 2, 1954, Serial No. 434,070

Claims. (Cl. 260-453) This invention relates to compositions of matter consisting essentially of a polymer containing at least 60 per cent of acrylonitrile in the polymer molecule, and a stabilizing agent to protect the polymer from the discoloring effects of exposure to light or heat.

Polyacrylonitrile and copolymers containing acrylonitrile as the predominant constituent undergo undesirable physical changes upon prolonged exposure to light or to heat. The observable symptoms of such changes include discoloration due in varying measure .to the action of either light or heat. Since the uses to which such polymers are put include the manufacture of molded articles and thin films, discoloration is to be avoided, if possible. To this end, it would be desirable to provide agents which can be admixed with the polymers to protect them against one or more of the adverse efiects of the conditions to which they may be exposed. The provision of stabilized compositions of the polymers and such protective agents is the principal object of the present invention.

This object is realized, according to the invention, by mixing with the polymer from 1 to 20, and preferably from 5 to 15 per cent by weight of a hydrocarbonoxypropionitrile having the general formula wherein R is selected from the group consisting of alkyl and alkylene radicals having from 1 to 3 carbon atoms, and n is 1 when R is alkyl and 2 when R is alkylene.

Articles made from the resulting compositions show little or no tendency to discolor upon prolonged exposure to ultraviolet light, especially when the stabilizer is present at concentrations of 5 per cent or more.

A copolymer of 80 per cent acrylonit-rile and 20 per cent isobutylene was prepared in aqueous emulsion, the polymeric particles were coagulated by addition of magnesium chloride solution, and the coagulum was washed and dried. This copolymer was found to be soluble to the extent of over 15 per cent by weight in acetone. In evaluating the various stabilizers, a 15 per cent solution of the copolymer in acetone was prepared, an amount of stabilizer equal to 15 per cent of the weight of copolymer was dissolved in the solution, and films were cast from the solution on glass plates. The films were dried in air overnight, then at 70 C. for one hour. The resulting films were mounted near the rim of a horizontal turntable, with half of the film covered and the other half exposed. The turntable was set in motion in a Fadeometer, and the exposed films were irradiated for 120 hours. The several films were then tested with a photoelectric reflection meter which had been set to read 100 when 2,760,950 Patented Aug. 28, 1956 turned toward a glazed white tile '(see footnote). An exposed but untreated film of the copolymer gave readings of about and had a light tan color, while the covered and unexposed portions of all the films gave readings of 90 to 96, using the white tile standard as a background.

Results with typical compounds in the recited class are given below:

Reflection meter read- Test Compound ing after 120 hrs. in

Fadeometer (Stabilizers):

None about 70. B-methoxypropionitril about 90 fl-ethoxypropionitrile. about 90 fl-n-propoxypropionitrile above fl-isopropoxypropionitrile above fl,fl-methylene di(oxypropionitrile) above 85 ,8,fi-ethy1ene di(oxypropionitri1e) above 85 fi,fl-1,2-propene di(oxypropionitrile) above 85. For contrast (non-stabilizers):

fl-hydroxypropionitrile about 70. Aeetonitrile l about 70. B-chloropropionitrile. under 70. Methylimidopropionttrll about 70. t3,fi-thiodipropionitrile about 70. fi,fi-sulfuryldlpropionltrile under 70.

Tests have shown that at least 1 per cent of the stabilizer is required to obtain significant protection from discoloration due .to heat or light, and that concentrations of from 1 to about 10 per cent are characterized by reflection values, after the light exposure test, between 80 and 85, while the compositions containing 11 to 20 per cent generally give reflection values, in the test, from about 85 to about 92. The stabilizers of this invention have little efiect on the brittleness of the polymeric product, and other additives must be employed to prevent embrittlement. Many such plasticizers are known in the art.

The problem of discoloration is not limited to the homopolymer of acrylonitrile, or to the specific copolymer of the example, and it has been found that the stabilizers of the present invention are efiective, as well, when incorporated in such acrylonitrile copolymers as 60-40 acrylonitrile/methyl acrylate; 86-10-4 acrylonitrile/isobutylene/allyl alcohol; 62.5-37.5 acrylonitrile/ vinyl acetate and -5 acrylonitrile/Z-vinyl pyridine.

We claim:

1. A composition of matter the essential constituents of which are a polymeric body selected from the class consisting of p-olyacrylo-nitrile and the copolymerization products of acrylonitrile only with other monoethylenically unsaturated comonomers, such copolymerizat-ion products containing at least 60 per cent by weight of acrylonitrile in the polymer molecule and, as a stabilizing agent therefor, from 1 to 20 per cent by weight of a hydrocar-bonoxypropionitrile having the general formula N0'rn.-In the Fadeometer employed, two type 8-4 General Electric Sunlight lamps are disposed horizontally and parallel to one another, with the centers ot the bulbs 4 inches apart, at a height 5.7 5 inches above, and displaced 6 inches from the center of a 1'2-ineh turntable driven at 33% revolutions per minute. The reflection meter used is a Model 610. made by the Photovolt Corporation, 95 Madison Ave., New York City, having a trlstimulus blue filter and set to read when turned toward a color-standard white ceramic Vitrolite" tile supplied by Gardner Laboratories, Bethesda, Maryland,

wherein R is selected from the group consisting of alkyl and alkylene radicals having from 1 to 3 carbon atoms, and n is 1 when R is alkyl and 2 when R is alkylene.

2. The composition claimed in claim 1, wherein the stabilizer is present in amount firom 5 to 15 per cent of the Weight of the polymer.

3. The composition claimed in claim 1, wherein the stabilizing agent is S-methoxypropionitrile.

4. The composition claimed in claim 1, wherein the stabilizing agent is fi-isopropoxypropionitrile.

References Cited in the file of this patent UNITED STATES PATENTS Downing et a1 Dec. 14, 1943 Crouch et a1. Aug. 19, 1952 

1. A COMPOSITION OF MATTER THE ESSENTIAL CONSTITUENTS OF WHICH ARE A POLYMERIC BODY SELECTED FROM THE CLASS CONSISTING OF POLYACRYLONITRILE AND THE COPOLYMERIZATION PRODUCTS OF ACRYLONITRILE ONLY WITH OTHER MONOETHYLENICALLY UNSATURATED COMONOMERS, SUCH COPOLYMERIZATION PRODUCTS CONTAINING AT LEAST 60 PER CENT BY WEIGHT OF ACRYLONITRILE IN THE POLYMER MOLECULE AND, AS A STABILIZING AGENT THEREFOR, FROM 1 TO 20 PER CENT BY WEIGHT OF A HYDROCARBONOXYPROPIONITRILE HAVING THE GENERAL FORMULA 